The "qRBBB" pattern

Presence of qRBBB in the setting of acute coronary syndrome signifies proximal occlusion of left descending coronary artery with compromise of circulation in the septal arteries supplying the bundle branches. Anterior STEMi with RBBB is associated with a higher risk of death when compared with that of patients with normal conduction. 

qRBBB with LAFBInstead of the rSR pattern (seen in RBBB), there is qRBBB pattern in V1 because the initial r wave has been knocked off by anterior wall myocardial infarction. 


Due to anterior location of the right ventricle than that of the left ventricle, activation of the right ventricular free wall can neutralize the abnormal septal forces associated with an anteroseptal MI. Therefore, in most patients with an anteroseptal infarction, abnormal Q waves in right precordial leads is mostly manifest during RBBB showing the classical qRBBB pattern, due to delayed activation of the right ventricle. 






Understanding RBBB

RBBB causes delayed depolarisation of right Ventricle as depolarisation spreads across the septum (instead of the Right Bundle) taking longer than usual. This produces characteristic ECG changes described below in the diagnostic criteria. Left Ventricle depolarisation remains normal i.e normal early part of QRS complex. 




Diagnostic Criteria 

  • Broad QRS > 120 ms
  • RSR’ pattern in V1-3 (‘M-shaped’ QRS complex) or a broad monophonic r wave or a qR complex
  • Wide, slurred S wave in the lateral leads (I, aVL, V5-6
  • Delayed intrinsicoid deflection time 


RBBB (Image from LIFTL)
RBBB often shows STD and TWI in V1-3 due to secondary depolarisation abnormalities 

Causes
  • Ischemic Heat Disease
  • Acute Pulmonary HTN (PE)
  • Chronic Pulmonary HTN (Cor Pulmonale)
  • Valvular Heart Disease
  • Myocarditis
  • Degenerative Diseases of conduction system
  • Congenital Heart Disease
  • Overdose of Na Channel Blockers
  • Idiopathic
  • Transient and Rate Related 

RBBB should NOT have any ST Elevation. Look for the qRBBB pattern and RBBB with LAFB (Leftward Axis, qR in lead I, aVL, rS in lead III) pattern. 

qRBBB in V1-4 with STE (Image from TheECGinAcuteMI)
Take Home:
  • Remember the qRBBB pattern morphology
  • RBBB should never have any ST elevation 
  • When in doubt, do serial ECGs and screening bedside ECHO to look for RWMA

References and Further Reading:
  1. Mishra, V., Sinha, S. K., & Razi, M. (2016). Right Bundle Branch Block: A Masquerader in Acute Coronary Syndrome. North American Journal of Medical Sciences8(2), 121–122. http://doi.org/10.4103/1947-2714.177347
  2. 2. Widimsky P, Rohác F, Stásek J, Kala P, Rokyta R, Kuzmanov B, et al. Primary angioplasty in acute myocardial infarction with right bundle branch block: Should new onset right bundle branch block be added to future guidelines as an indication for reperfusion therapy? Eur Heart J. 2012;33:86–95.
  3. Ganesan S, Kannan K, Victor A, Selvan KT, Arun R, Majella JC, Kumar RS, Aravind A, Viswanathan N, District V. QRBBB in acute coronary syndrome: Does it matter in modern era? Angiographic correlation. Indian Heart Journal. 2015 Dec 1;67:S38.
  4. Wong CK, Stewart RA, Gao W, French JK, Raffel C, White HD. Prognostic differences between different types of bundle branch block during the early phase of acute myocardial infarction: Insights from the Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial. Eur Heart J. 2006;27:21–8. 
  5. http://hqmeded-ecg.blogspot.co.uk/2010/01/right-bundle-branch-block-with-subtle.html
  6. http://hqmeded-ecg.blogspot.co.uk/2017/04/rbbb-with-transient-st-elevation.html
  7. http://hqmeded-ecg.blogspot.co.uk/2010/11/wide-complex-tachycardia-its-really.html
  8. http://hqmeded-ecg.blogspot.co.uk/2014/03/elderly-woman-in-shock-ekg-from.html
  9. https://emcrit.org/wp-content/uploads/2015/03/Who-to-PCI-by-Smith-and-Weingart.pdf
  10. https://lifeinthefastlane.com/ecg-library/basics/right-bundle-branch-block/

Posted by:

              
     Lakshay Chanana
     
     Speciality Doctor
     Northwick Park Hospital
     Department of Emergency Medicine
     England

     @EMDidactic

    Croup – Laryngotracheobronchitis

    Viral Laryngotracheobronchitis (Croup) is the most common cause of stridor commonly affecting children between 6 months to 6 years old, with a peak in the fall and early winter months. Croup is acquired through inhalation of the virus. 

    Possible agents could be parainfluenza virus (most common), rhinovirus. enterovirus, respiratory syncytial virus, influenza virus and human metapneumovirus.


    Clinical Presentation 
    Typically, symptoms begin after 1 to 3 days of URTI symptoms (nasal congestion, rhinorrhea, cough, and low-grade fever). Classic symptoms include a harsh barking cough, hoarse voice, and stridor. Symptoms often tend to be worse at night and the severity of symptoms is related to the amount of edema and inflammation of the airway. 


    Diagnosis and Assessment of Severity 
    Look for tachypnea, stridor at rest, nasal flaring, retractions, lethargy or agitation, and oxygen desaturation. Symptoms are most severe on 3rd or 4th day of illness. Agitation and crying increase oxygen demand and may worsen airway compromise. Bloods and imaging are only required in children who fail to respond to conventional therapy. X Rays may demonstrate “steeple sign” (subglottic narrowing)


    Steeple Sign
    Croup is a clinical diagnosis
    Steeple sign may be present in normal children and can be absent in up to half of those with croup






















    Management 
    Treatment is directed at decreasing airway obstruction and keeping the child comfortable 
    • CorticosteroidsAll patients with croup get steroids as a one- time dose (PO/IM/IV). Steroids reduce the severity and duration of symptoms and result in a decrease in return visits and hospital length of stay. The long half-life of dexamethasone (36-54 h) often allows for a single injection. Studies have shown that dexamethasone dosed at 0.15 mg/kg is as effective as 0.3 mg/kg or 0.6 mg/kg (with a maximum daily dose of 10 mg). Effects can be seen within 1 hour of oral administration. Nebulized budesonide 2 mg as a single dose and IM dexamethasone (0.6mg/kg) are alternatives to PO dexamethasone in children who are vomiting.
    Treatment of croup: Nebulized epinephrine for moderate to severe croup and corticosteroids for all



    • EpinephrineEpinephrine comes as two different forms: racemic, which is composed of equal parts of L- and D-isomers, and L-epinephrine, which is the drug routinely used in acute situations in concentrations of 1:1000 and 1:10,000. 
    • L-Epinephrine (1:1000): 0.5 ml/kg neb or 5ml maximum  
    • Racemic Epinephrine (2.25%): 0.05ml/kg neb or max 0.5ml
    Mild croup generally does not require epinephrine. For those with moderate or severe croup who receive nebulized epinephrine, observe in the ED for at least 3 hours before considering discharge. Epinephrine decreases airway edema through vasoconstrictive alpha effects and acts wishing 10-min lasting up to 2 hours. The use of Adrenaline decreases the number of children with croup requiring intubation, ITU admissions, and admission to the hospital. 

    Observation for about 3 hours is recommended because an increase in croup scores can occur between doses of epinephrine nebulisation

    • Intubation is reserved for cases of severe croup not responding to medical treatment. When intubation is necessary, use endotracheal tubes smaller than recommended for patient size and age to avoid traumatizing the inflamed mucosa. 

    Treatment options with limited evidence: 
    • Cool Mist: Humidified air was used to treat croup, but they are no longer recommended as studies have consistently failed to show clinical improvement with these interventions.
    • Heliox (70% helium/30% oxygen): Despite its theoretical benefits, studies show no definitive advantage of heliox over conventional treatment.24-28
    • Beta 2 Agonists: Insufficient data. Concerns about risk of worsening upper airway obstruction as β-receptors on the vasculature cause vasodilation (as compared to the vasoconstrictive α effects of epinephrine), which might worsen upper airway edema in croup, and there is no smooth muscle in the upper airway. Therefore, β-agonists are not recommended for treatment of croup.
    • Antibiotics have no role in uncomplicated croup 
    • Antitussives have no proven effect on the course or severity of croup and may increase sedation


    Differential Diagnosis (Consider if no relief with Rx)
    • Bacterial tracheitis
    • Laryngomalacia
    • Tracheomalacia
    • Vascular rings
    • Epiglottitis (unlikely if vaccinated)
    • Foreign body aspiration
    • Peritonsillar abscess
    • Retropharyngeal abscess
    • Tracheo-esophageal fistula

    Admit 
    • Moderate to Severe Croup
    • Looking toxic and not tolerating oral fluids
    • Comorbidities 
    • Social Issues
    • Persistent stridor at rest, tachypnea, retractions, and hypoxia

    Discharge Advice 

    • Advise the parents/carers to use either paracetamol or ibuprofen to treat a child who is distressed due to fever. 
    • Encourage the child to take fluids regularly.
    • To check on the child regularly, including through the night.

    References and Further Reading :
    1. https://cks.nice.org.uk/croup#!scenario
    2. http://www.ebmedicine.net/topics.php?paction=showTopic&topic_id=334
    3. Russell KF, Liang Y, O’Gorman K, Johnson DW, Klassen TP. Glucocorticoids for croup. Cochrane Database of Systematic Reviews 2011, Issue 1. Art. No.: CD001955.
    4. Johnson DW. Croup. BMJ Clin Evid. 2009; 2009: 0321.
    5. Bjornson, C.L. and and Johnson, D.W. (2013)  Croup in children. CMAJ. 185(15), 1317-1323

      Posted by:

                    
           Lakshay Chanana
           
           Speciality Doctor
           Northwick Park Hospital
           Department of Emergency Medicine
           England

           @EMDidactic


        

        

    Benzodiazepine Overdose

    Benzodiazepines work through GABAa receptors and this class of medications are commonly used in Emergency Department to aid sedation, anxiolysis and amnesia. IV administration may result in significant complications, particularly respiratory depression and hypotension, especially when combined with opioids or other sedatives.


    Alternatively, BZDs are also used as first line anticonvulsants. Patients with mental health issues are often given this set of medications to treat concomitant anxiety and thus overdose is frequently a problem. Fortunately, isolated benzodiazepine overdose has low mortality and fatalities are rare. In cases of mixed overdose i.e combination with TCAs and opioids, complication rates are higher. Out-patients use of BZDs is limited to short-term treatment of anxiety and insomnia.




    Clinical Presentation (think EtOH intoxication)
    • Typical - Slurred speech, Drowsiness, Stuporous, Confusion, Ataxia, Incoordination and Coma
    • Paradoxical reactions - Excitement, Anxiety, Aggression and delirium are more commonly seen in hyperactive children and psychiatric patients


    Treatment
    • Maintain ABCs
    • Use Flumazenil if no contra-indications 
    • Wait for the drug to wear off

    Consider activated charcoal in case of early presentations and have a secured airway prior to that. It is debatable to intubate someone with a BZD overdose coming with a low GCS (say E1M5V1) with isolated BZD overdose. Make a decision in liaison with ITU team as there is a clear and reversible cause of low GCS. However, this needs to weighed against risk of aspiration if the patient vomits. 

    Flumazenil is a selective antagonist of the central effects of benzodiazepines. It should be used only in two scenarios:
    • Definite isolated BZD overdose in naive BZD user
    • Reversal of iatrogenic benzodiazepine induced sedation (see contra-indications below)
    Recurrent benzodiazepine toxicity may result once the effects of flumazenil have worn off.  Flumazenil Dose: 0.2 milligram IV q1min up to a total dose of 3 milligrams

    Contraindications to Flumazenil:
    • Chronic BZD users
    • Mixed Overdoses (esp TCA)
    • Seizure Disorder
    • Suspected raised ICP
    Flumazenil induced seizures should be treated with other GABAA receptor agonists (propofol and phenobarbitone) because the benzodiazepine site on the receptor is antagonised. 


    Admit if:
    • Persistent drowsiness
    • Respiratory depression
    • Hypotension

    Take Home:
    • Definite indication of Flumazenil is iatrogenic overdose of BZD
    • Mortality is low with isolated BZd overdose --> Maintains ABCs and wait for the drug to wear off
    • Reduce dose to half when sedation elderly 

    References:


    1. Ngo AS, Anthony CR, Samuel M, Wong E, Ponampalan R: Should a benzodiazepine antagonist be used in unconscious patients presenting to the emergency department? Resuscitation 74: 27, 2007. 
    2. Charlson F, Degenhardt L, McLaren J, et al: A systematic review of research examining benzodiazepine-related mortality. Pharmacoepidemiol Drug Saf 18: 93, 2009

    Posted by:

                  
         Lakshay Chanana
         
         Speciality Doctor
         Northwick Park Hospital
         Department of Emergency Medicine
         England

         @EMDidactic